Indira Gandhi in 1983 – her assassination the next year is the subject of a controversial new film. Photograph: Reginald Davis/REX

India’s intelligence agency has warned of potential violence around the release of Kaum De Heere, a Punjabi film which portrays the assassination of India’s former prime minister Indira Gandhi.

The film tells the story of her assassins, Sikh bodyguards who turned against Gandhi following Operation Blue Star, a military operation to quell revolution in Amritsar in 1984 which left hundreds of Sikhs dead. One of the bodyguards, Beant Singh, was killed by police shortly after, while the other, Satwant Singh, was later hanged.

Director Ravinder Ravi claims that the film is not biased, and that it merely tells the story as drawn from the trial of Kehar Singh, one of the plotters, as well as the confessions of the assassins themselves. “Allegations that we want to create a law and order problem by showing what happened 30 years ago are meaningless,” Ravi told the Times of India. “We are just reproducing what has been documented. What’s wrong in bringing historical incidents before the public after 30 years?”

Protests are nevertheless being planned by the Punjab Youth Congress, a youth political organisation who claim the film glorifies the assassins. “The movie not only justifies the killing of the former PM, but is also an attempt to revive terrorism in Punjab,” said congress president Vikramjit Singh Chaudhary. “We hope the [current] PM [Narendra Modi] will intervene in the issue. Otherwise, we would not allow the film to be released in Punjab ... the government shall be responsible for any law and order issue that may crop up.”

The son of one of the killers, Sarabjit Singh Khalsa, has championed the film, saying: “The movie brings to fore the pain which Indira’s bodyguards felt during their visit to the Golden Temple after Operation Blue Star.”

The chief minister of the Punjab, Parkash Singh Badal, has said that he would ask India’s home secretary to look into the situation. Kaum De Heere is set for release on Friday.